Bus clamp



July 12, 1932. A, ALSAKER 1,867,130

BUS CLAMP Filed April 29. 1927 2 Sheets-Sheet l July l2, 1932.

A. ALSAKER BUS CLAMP Filed April 29. 1927 2 Sheets-Sheet 2 vJuUee/ZZ2925 5 35 @Qa/Kef. m@ Jua# Patented July `12., 1932 UNITED STATES PATENT OFFICE ALFRED ALSAKEB, OF CHICAGO, ILLINOIS, ASSIGNOR TO THF DELTA-STAB ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS BUS CLAMP application aled april 29,

tangular section because of the ease of working and because of superiory cooling ability.

In joining such bars to each other or to other 'fao bars the accepted practical method is to clamp them mechanically, as by bolts and clamping plates. For mechanical rigidity and chiefly for electrical conductivity, it is desirable that the faces of the parts to be joined be uniformly in contact under a relatively high pressure. l

kI have found that the unit pressure relquired to make a satisfactory joint is dependent upon the current to be carried, that is, upon current density of the oint.

Prior to this invention flat clamping plates have been used. These plates overlap or overhang the edges of the parts to be joined and both draw these overhanging edges together. The plates of the prior art are provided with flat faces, and when it is attempted to'vdraw the plates tight against the bars, the plates spring under the pressure and the edges of the plate bite into the metal of the bar. While a total pressure is thus secured of as'high a value as may be desired, the distribution of the pressure is not proper and the joint does not have the desired conductivity and it tends to overheat.

According to the present invention the clamping plates are so constructed as to give a uniform pressure over their faces when drawn tight. I take advantage of the elas-iv ticity of the plates by making the face of the fof Figure 19 taken on the line v19---19 showclam convex and the degree of convexit j together with the character of the material employed, and the area of contact-to be secured are so inter-related and coordinated that when the .clamp is drawn tight the plate is sprung or pressed to bring the convex flat face substantially into, a`plane. This auto? matically provides the proper clamping pres, sure. The clamps are Ifotl pressed beyond the elast-ic limit and hence when pressure upon them is released they' assume the original 1927. serial No. 187,671.

pherical or convex shape on the workingI ace. l

Now in lorder to acquaint those skilled in the art with the mannerof constructing and operating a device according to my invention, I shall describe in connection with the accompanying drawings a specific embodiment of the same.

In the drawings,-

Figures 1, 2, and 3 are with in the practice of joinin bars;

Figure 4 is a front elevat1onal view of a clamping plate embodying my invention;

Figure 5 is an end elevational view looking at the right end of Figure 4;

Figures 6, 7 and 8 are sections taken on the lines -s, 77, and 8-f8 of Figure 4, respectively;

Figure 9 is a face view of a straight or two bolt clamp;

rFigure 10 is a rear elevation of the same;

Figure 11is a longitudinal vertical section taken on the line 11-11 of Figure 9;

Figure 12 is a transverse section taken on the line 12-12 of Figure 10;

Figure 13 is a rear view of of four bolt clamp;

Figure 14 is a left Figure 13; Figures 15 and 16 are sections taken, respeca modified form end elevational view of Figure 13 Figure 17 is a face view ofa modified two bolt clamp of my invention; t

Figure 18 is a rear view of another modified` form of two bolt clamp;

Figure 19 is a rightslde elevational view ing the lower part of the same in section;

Figure 20- is a longitudinal vertical section of the clamp shown in Figure 18;

diagrams explainingV f f the types of joints which are commonly met tively, on the lines 15-,15 and 16-16, of`

bronze, in ,order to secure high mechanical strength, relatively good electrical conductivity, and low cost of manufacture, it is to be understood that the clampsmay be made of sheet metal suitably stamped in a forming die, or dies.

' these clamps are literally loading springs.y`

theentire flow of current must It is tov be observed fundamentally that While they appear to be rigid cast metal they are, as a matter of fact, springs of great v stiffness and small flexure or throw. Also, whereas I describe herein a convex or spheri: cal clamping or engaging face, it is not essential that the convexity of the facebe strictly spherical, and I consider as commg within my invention any clampmg plate the clamping surface of which is convex whether or not the convex surface is spherical or of specifically different curvature.

The amount of current which flows through a joint where the clamp is used 1n making a joint determines in some degree the pressure which must be applied between the bars to be joined.

Most joints in bus bars are made in stralght runs, that is, 180 joints, or in taps, that 1s, 90 joints.

In Figures 1, 2 and 3 I have illustrated t ical joints which are to be made. Assume t at the longitudinalbar 1 is to be joined to the vertical tap 2 and that the area of the ljoint is, therefore, the width A of the bar 1 1n one dimension, and the width B of the bar 2 inthe other dimension. Assume that in this case the two bars are of equal width, that is, A equals B. Such a joint is made where the same current which Hows through the bar 1 may flow througll the bar 2 and as a result pass through the joint.

In case 2,'Figure 2, the main run of bus 1s shown inthe horizontal bar 3 and the tap is taken oi as bar 4 which in this instance is of half of the width of the bar 3. In this case A equals 2-B. This joint is designed so thatI the current owing in the bar 3 only a portion, in this case one-half, is to be taken off in the ta 4.

In the'case illustrated in Figure 3, the longitudinal run of bus bar 5 is connected to a vertical .tap 6 and the vertical tap is designed to take current from both directions, or vice versa, to deliver current in both directions with respect to the'bar 5. In this case it will be seen that the superficial area of the joint may be the same in Figures 2 and 3, but th'e current density in Figure 3 is twice the current density in Figure 1. The current densltv'of the joint in Figure 2 is the same as that 1n lgure 1. g v

The proper pressure has been found by ex shown in Figure 2, even though mechanically the same superficial area and dimensions of the joint occur.

The present line of clamps has, therefore, been designed with a convex face and of suitable strength so that when the clamping plate or clamp is attened down against the bar, the correct pressure is obtained, and this correct pressure in termsof unit pressure of pounds per square inch is reckoned according to the yfollowing equation:

In the above equation B re resents the tap and A represents the run of us ininches of width.

In Figure 4 I have illustrated. a clamping plate such as is suitable for clamping together the bars 1 and 2 in Figure 1. f

This structure comprises an open rectangular frame member having the sides thereof formed of bars 7, 8, 9, 10 with integral bolting lugs 11 at the corners thereof, and with cross intersecting bars 12, 12 lying within the open frame. The section of the side bar 10 is shown in Figure 6 as comprising an L-shape consisting of a relatively narrow vertical ange 13 and a horizontal flange 14, the lower surface of which at 15 partakes of the convexity with-which the engaging or contacting face of the clamp is constructed. In Figure 5 the convexity of thecoutacting face 16 is indicated by the dotted line 17, which dotted line indicates a plane between the corners of the active face of the clamp. This plane 17 indicates theoretically the position into which the convex face is forced when the clamp is under full clamping pressure. As a matter of fact, the bars themselves are also suiciently elastic to have considerable give with the result that the convexity of the plate does not altogether disappear, but the proper clamping pressure of the plate with respect to the bars to be -joined is 1ndicated when the edges of the plate are tight Unit pressure= against the edges of the bar, so that a feeler,

-prising a vertical flange 18 and a horizontal flange 19, the lower surface of vex as ndicatedat 20.

In the embodiment of Figure 13 a dierent which is conform of square clamp is illustrated. The general outline of the clamp is the same.l It comprises the open rectangular frame having the side members 21 which are of a section, as shown 1n Figure 16. It also includes the cross diagonal ars 22 which are of an inverted U-shape section as shown in Figure 15. The bearing faces 23 and 24, respectively, of the bars 21 and 22, are convex as explained in connection with the previous embodiment. Integral bolting lugs 11, 11 are provided at the corners for applying pressure to thebars to be clamped. It is to be noted in this modifica-tion that the metal is used to slightly bet-y ter advantage so that for a given weight of material it secures relatively greater rigidity and hence greater pressure. The clamp shown in Figure 4 is a heavy duty clamp and, 'as will be seen by comparing the radius of curvature, the clamp of Figure 4 is intended to apply greater pressure clamped than is the plate of Figure 13.

' the full length The curvature on the contact face of the clamp issecured by grinding the same on a concave grinding wheel. The radius of curvature varies from 25 feet to 35 feet, depending upon the area of the clamp and other factors. These other factors include the elasticity of the metal, that is, Youngs modulus, the dimensions of the clamp section, the number of bolts used to secure the clamping effect, and the areas to be clamped'. The di mensions of the .clamp section are designed to withstand the 4total deflection at full pressure without vexceeding the elastic limits of the material employed. These clamps may be made of bronze and of malleable iron. Other materials may be used if desired.

Instead of using a four bolt rectangular clamp a three. bolt triangular clamp may be employed. The principles upon which the same are constructed and the mode of-operation are the same as above described. v

Where it is desired to clamp a number of bars together with spacers between them to prevent vibration, and the like, a two bolt clamp may be employed. In the device of Figure 9 the body of the clamp is relatively narrow and has the bolting lugsll, 11 at the ends with the intermediate sections in the form of any inverted U, as shown in Figure 12. The two legs 26, 26 are convex at their lower ends as indicated at 27 and at their upper ends are joined by the web 28 which extends f the clamp.

In Figures 17, 19, and 21 I have indicated a heavy duty clamp such as may be employed for wider bars lor for greater pressure, this bar consisting of the bolting lugs 11 atthe ends andan intermediate section which comprises a central web 29 with the raised anges 30, 30 on the outside thereof, extending flanges 31 widerI at the vcenter than at the ends with the ribs 32 on thel engaging or clamping face, which ribs which are ground to the bars to beA to the convex form desired. The tension flanges 30, 30 are thus placed substantially mid-way between the compression ribs 32, 3 2 to get an even distribution of pressure.

In .Figures 18, 20 and 22, I have shown a heavy duty clamp similar to the clamp shown in Figure 9, which includes the bolting lugs 11,11 at the center and a lozenge shaped body, comprising three webs 83 joined by the plate 34.*, The webs 33 are convex at their free edges 35 to bear upon the bars to be clamped. In the joint shown in Figure 1, a clam such as shown in Figure 4 or 13 is employe the bolting lugs 11 falling outside the edges of the bars to be clamped with whatever `working clearance is required. For making the joint shown in Figure 2 either a triangular clamp or oblong rectangular clamp may be employed, and for Figure 3 an oblong rectangular clamp is preferably employed.

While I have described theclamp of my invention as employed primarily for making joints between bars, it is to be understood that these clamps may be employed merely for holding bars together or for holding bars upon sup orts, as on insulators and the like.

,It will e seen that the clamp of my invention is highly advantageous in that the pressure is first applied centrally and then is distributed outwardly from the center by the springing of the plate. The clamp serves as an automatic indicator of the right pressure, since the inherent design of the plate employed in`each particular case is such that when the convex face has been' deflected to a point where the entire surface of the same is in engagement with the flat bar, the proper pressure has thereby been secured and further tightening of the bolt is not required.

In the specific forms which I have illustrated and described the en aging face is convex and the opposite side at. The plate may be concave on the back or otherwise formed. While I have shown an open frame or skeletonized plate, and while I find the same advantageous, it is not essential. It is found that thin metal sections and an open frame 'give greater strength for a given weight of metal.

By the term double convexity as used in the claims I mean a surface convex in all di- .limit of the metal to deflect the same into contact with a fiat surface with which the same engages.

2. A clamping late for bus bars and the for clamping i like comprising a resilient cast metal plate having a convex face for engaging the bus bar, and lugs along the margins of said plate for pressing the plate against the bus bar until the convex face is substantially flattened, the portion ofthe plate between any lug and its adjacent lugs being convex when the plate is unclamped.

3. A clamping plate for clamping bus bars and the like comprising a metal plate substantially flat on one side and substantially spherical on the other side, and of a radius of curvature such as to permit delection of the spherical side to a substantially at surface by a force below the elastic stress limit of the metal.

4. In 'combination with a pair of bus bars, means including a spring clamping plate for clamping the bus bars, said clamping plate comprising an elastic convex plate of double convexity, the convex face thereof being delected by a relatively great force into planar contact with the surface with which it engages, the metal of the plate being stressed below its elastic limit by the deiection, and the force deecting the plate exerting the clamping pressure between the bus bars.

In witness whereof, I hereunto subscribe my name this 27 th day of-April, 1927.

ALFRED ALSAKER. 

